The use of lumen-side feed inside-skinned polymeric composite hollow fiber membranes for reverse osmosis applications is disclosed in commonly-assigned U.S. application Ser. No. 702,421 filed Feb. 13, 1985, now abandoned. In reverse osmosis (RO) applications, the internal burst pressures of the hollow fiber supports of such composite membranes constitute a critical factor in the performance of the fibers; in general, the higher the internal burst pressure of a given hollow fiber support, the better the RO performance of the composite membrane will be. In RO applications for desalination of sea water, for example, due to the high osmotic pressure of sea water itself, dynamic or operating pressures in the neighborhood of 800 psi are required. However, with conventional casting techniques, hollow fibers with operational burst strengths of only around 400 psi are obtainable. In addition, hollow fibers having high water permeability are highly desirable in RO applications.
There is therefore a need in the art for hollow fibers capable of greater operational internal burst pressures than are obtainable with conventional casting techniques. There is also a need in the art for hollow fibers having increased water permeability. These needs and others are met by the process of the present invention, which is summarized and described in detail below.